The notes, which retain the image of American statesman and scientist Benjamin Franklin, include two new security features – a blue three-dimensional security ribbon with images of bells and 100s, and a color-changing bell in an inkwell, the Fed said in a statement.

The bills, known as Benjamins, also keep security features from the previous design, such as a watermark.

“The new design incorporates security features that make it easier to authenticate, but harder to replicate,” said Federal Reserve Board Governor Jerome Powell said in a statement.

The security features will let users verify the notes’ authenticity more easily, he said.

U.S. officials have said the $100 note is the most frequently counterfeited denomination of U.S. currency outside the United States due to its broad circulation overseas. In the United States, the $20 bill is the most frequently counterfeited note.

Benjamins are the highest-denominated notes issued by the Federal Reserve, since the United States stopped issuing $500, $1,000 and $10,000 notes in 1969.

The new bills have been in development since 2003.

People with old bills do not need to trade them in for new ones since all designs of U.S. currency remain legal tender, the Fed said.